This invention relates to the use of combinations of PGF.sub.2.alpha. and PGE.sub.2 prostaglandins and derivatives thereof in the treatment of glaucoma and ocular hypertension. PGF.sub.2.alpha. and PGE.sub.2 and their respective derivatives are represented by formulae (I) and (II) respectively: ##STR1## wherein R.sub.1 is hydrogen, a cationic salt moiety, a pharmaceutically acceptable amine moiety or a pharmaceutically acceptable ester moiety derived from the corresponding alcohol; and R.sub.2 is hydrogen or a pharmaceutically acceptable ester moiety derived from the corresponding carboxylic acid.
Natural prostaglandins are known to lower intraocular pressure (IOP) after topical ocular instillation, but can cause an inflammatory response. Many synthetic prostaglandins have been observed to lower intraocular pressure, but most such compounds also produce the described inflammatory response. It has been unexpectedly discovered that dosing with a combination of prostaglandins of formulae (I) and (II) produces a greater reduction of IOP than the equivalent dose of either compound given separately. In fact, as described in greater detail below, representative mixtures of prostaglandins (I) and (II) produce a profound and long lasting IOP decrease, even though the same dose of the PGE.sub.2 component produced only a modest short decrease and twice the dose of PGF.sub.2.alpha. produced no significant decrease in the primate model. Administration of both prostaglandins (I) and (II) is apparently necessary to produce the desired IOP lowering effect for glaucoma therapy. The requirement for two different prostaglandins to be present in the eye in order to achieve optimum IOP reduction has not been described before.